1. Field of the Invention
This invention relates to a cleaning roller system preferable for use in a printer having a printing head (thermal head) and an operating method thereof.
2. Description of the Related Art
Some of thermal head type printers utilize a thermal transfer type ribbon (toner ribbon) as recording material. As shown in FIG. 7, for example, this type of printer comprises a thermal head 1, a platen 5 disposed so as to oppose a resistive heating element 3 on the thermal head 1, a toner ribbon 7 to be interposed between the thermal head 1 and the platen 5 and to be wound up from a feeding side 7a to a winding side 7b, a guide roller 9 for guiding the toner ribbon 7 and a pair of pinch rollers 11 at an exit from the thermal head 1 and the platen 5. A recording sheet 13 is overlapped with the toner ribbon 7 and inserted between the thermal head 1 and the platen 5. Then, dots in the resistive heating element corresponding to an image to be printed are selectively heated so as to perform thermal transfer from the toner ribbon 7, so that the image is transferred to an image receiving plane of the recording sheet 13.
Further, some of thermal head type printers transfer an image directly to a heat sensitive film which is a recording material without use of the toner ribbon 7. This type of printer, as shown in FIG. 8 for example, comprises a thermal head 1, a platen 5 disposed so as to oppose the resistive heating element 3 of the thermal head 1, and a pair of pinch rollers 11 disposed at an exit from the thermal head 1 and the platen 5. A heat sensitive film 15 which is a recording material is inserted between the thermal head 1 and the platen 5. Then, dots in the resistive heating element corresponding to an image to be printed are selectively heated so as to produce colors directly on the heat sensitive film 15 thereby obtaining the image.
In the conventional printers shown in FIGS. 7 and 8, the toner ribbon 7 or the heat sensitive film 15 is fed with being interposed between the thermal head 1 and the platen 5 and then a desired image is obtained on the recording sheet 13 or the heat sensitive film 15.
However, because the resistive heating element 3 of the thermal head 1 keeps in contact with a recording material upon transferring heat, if a foreign matter adheres to the recording material before it reaches the resistive heating element 3, the foreign matter carried with transportation of the recording material is caught by the resistive heating element 3. Contact between the resistive heating element 3 and the recording material is lost at that position so that black portion (i.e. line void) may be generated where the foreign matter passes in the recording material because thermal transfer is not realized there.